<!DOCTYPE html>
<html>
<head>
  <style>
    #checkbox {
       position: absolute;
       left: 0px;
       top: 0px;
       background: -moz-linear-gradient(left, white, brown);
    }
  </style>
</head>
<body>
  <div id="checkbox">
    <input type="checkbox">
  </div>
</body>
</html>
